This invention relates to a method and means for avoiding collision between a driven motor vehicle and obstacles lying in its path.
It is known that a high percentage of accidents could be avoided by anticipated reaction by the driver. As a consequence various anti-collision systems designed to monitor the environment surrounding the motor vehicle and to indicate the presence of obstacles to the driver, in particular under conditions of poor or reduced visibility, typically as a result of fog, but also as a result of lack of attention by the driver, have already been investigated and proposed for a number of years.
In particular various systems, either of the passive type, such as television cameras, which however have the disadvantage that they require complex computing for the determination of distance, and of the active optical type, such as laser devices, which are however subject to atmospheric absorption, in particular in fog, and above all microwave radar, which has better properties than the other systems in that it provides the distance to the objects found directly, with barely any atmospheric absorption, have been proposed for the detection of obstacles.
The simplest known arrangements are of the fixed beam type with straight-line observation of the area of the road in front of the vehicle. These arrangements have proved to be of little reliability and are subject to numerous errors, particularly on bends, because of the inability of the system to distinguish obstacles which actually lie in the vehicle's path from objects which lie in a straight line in front of the vehicle but not in its path, such as trees growing by the edge of the road on a bend or vehicles travelling in the opposite direction (as is for example shown in FIG. 1, in which a vehicle 1 travelling in direction 2 on a section of road 3 mounting a fixed beam system would see vehicle 5 travelling on section of road 6 on the opposite carriageway and in direction 7 as an obstacle).
In order to overcome the problems mentioned above, other known arrangements provide for the possibility of orientating the beam on the basis of the angle of the steering wheel and others also provide for the scanning of circular sectors ahead of the vehicle on the basis of the steering wheel angle. However even these arrangements yield a high number of false alarms, as again made clear in the example in FIG. 1. In fact, as is known, when vehicle 1 explores the area of road which extends along a line of circumference indicated by dashed line 8 corresponding to the manoeuvre initially brought about by means of the steering wheel, objects which are placed at the edge of the road at the point indicated by 9, or right off the road, are identified as obstacles, when in fact there is no obstacle in the real path of the vehicle indicated by dashed line 10.
In an attempt to eliminate these disadvantages special arrangements, such as the use of complex filters based on the relative speed of an obstacle in such a way as to delay the alarm and permit further observation, which only solve part of the problem of false alarms and do not offer a sufficient level of reliability, have been investigated.
Known systems also provide various arrangements for attracting the driver's attention to the alarm situation detected, using displays which in general provide for the illumination of predetermined luminous icons of different colour and size depending on the level of the alarm, accompanied by signals of an acoustic type. However even these known types of display have proved to be insufficiently effective and also restricted, in that they do not provide information on the transverse dimensions and position of the obstacle with respect to the road, and therefore on the scope for avoiding the obstacle by means of a suitable manoeuvre.